Logico-numerical Control for Software Components Reconfiguration

International audienceWe target the problem of the safe control of reconfigurations in component-based software systems, where strategies of adaptation to variations in both their environment and internal resource demands need to be enforced. In this context, the computing system involves software components that are subject to control decisions. We approach this problem under the angle of Discrete Event Systems (DES), involving properties on events observed during the execution (e.g., requests of computing tasks, work overload), and a state space representing different configurations such as activity or assemblies of components. We consider in particular the potential of applying novel logico-numerical control techniques to extend the expressivity of control models and objectives, thereby extending the application of DES in component-based software systems. We elaborate methodological guidelines for the application of logico-numerical control based on a case- study, and validate the result experimentally

Behavioural Model-based Control for Autonomic Software Components

International audienceAutonomic Managers (AMs) have been largely used to autonomously control reconfigurations within software compo- nents. This management is performed based on past monitoring events, configurations as well as behavioural programs defining the adaptation logics and invariant properties. The challenge here is to provide assurances on navigation through the configuration space, which requires taking decisions that involve predictions on possible futures of the system. This paper proposes the design of AMs based on logical discrete control approaches, where the use of behavioural models enriches the manager with a knowledge not only on events, states and past history, but also with possible future configurations. We define a Domain Specific Language, named Ctrl-F, which provides high-level constructs to describe behavioural programs in the context of software components. The formal definition of Ctrl-F is given by translation to Finite State Automata, which allow for the exploration of behavioural programs by verification or Discrete Controller Synthesis, automatically generating a controller enforcing correct behaviours. We implement an AM by integrating the result of Ctrl-F compilation and validate it with an adaptation scenario over Znn.com, a self-adaptive case study

Discrete Control of Response for Cybersecurity in Industrial Control

International audienceCybersecurity in Industrial Control Systems (ICS) is a crucial problem, as recent history has shown. A notable characteristic of ICS, compared to Information Technology, is the necessity to take into account the physical process, and its specific dynamics and effects on the environment, when considering cybersecurity issues. Intrusion Detection Systems have been studied extensively. In our work, we address the less classic topic of response mechanisms, and their automation in a self-protection feedback loop. More precisely, we address self-protection seen as resilience, where the functionality of the system is maintained under attacks, be it in a degraded mode. We model this as a Discrete Event Systems supervisory control problem, involving a model of the plant's possible behaviors, a model of considered attacks, and a formulation of the control objectives. We consider a case study, and perform a prototype implementation and simulation, using the Heptagon/BZR programming language and compiler/code generator, and targeting a multi-PLC experimental platform

Symbolic Abstract Heaps for Polymorphic Information-flow Guard Inference (Extended Version)

In the realm of sound object-oriented program analyses for information-flow control, very few approaches adopt flow-sensitive abstractions of the heap that enable a precise modeling of implicit flows. To tackle this challenge, we advance a new symbolic abstraction approach for modeling the heap in Java-like programs. We use a store-less representation that is parameterized with a family of relations among references to offer various levels of precision based on user preferences. This enables us to automatically infer polymorphic information-flow guards for methods via a co-reachability analysis of a symbolic finite-state system. We instantiate the heap abstraction with three different families of relations. We prove the soundness of our approach and compare the precision and scalability obtained with each instantiated heap domain by using the IFSpec benchmarks and real-life applications

The Breakdown to Turbulence of a Forced Vortex Flow at a Pipe Orifice: The Non-Linear Evolution of Initially Axisymmetric Vortices

The primary purpose of this research is to investigate non-linear and chaotic behaviour of water in a pipeline at the transition region from laminar to turbulent flow. Turbulence was generated in the flow by the use of an orifice plate which generated coherent vortices and subsequent break-down into turbulence, downstream of the orifice. The flow regime was pulsatile. This was decided specifically to obtain better control of the experimental apparatus, better control of the frequency of vortices shedding from the orifice, and because of its wider range of practical applications discussed in section 1.3. The mechanism of vortex breakdown has been addressed many times over the past century. The process by which vortices interact and degenerate is essentially non- inear. New techniques from the field of non-linear dynamics have emerged which can yield some quantitative information about the complexity of non-linear phenomena. This thesis aims to test some of these techniques, together with more traditional methods, on the experimental time series data obtained from axisymmetric vortex breakdown of a pulsed flow at a pipe orifice. An experimental rig was designed and constructed in the Civil Engineering Department, at the University of Glasgow, to produce, accurately controllable, pulsed flows within a pipe system at an orifice plate. The apparatus was designed to allow a range of parameters to be varied over the course of the investigation. Computer algorithms were written by the author to analyse the resulting data, obtained from Laser Doppler Anemometry readings. Flow visualisation techniques were also used to give a qualitative understanding of the system. Evidence was found for the development of initially axisymmetric pulsed vortex flows to a relatively low dimensional chaotic state prior to breaking down to a more complex turbulent state. The flow complexity was probed by investigating the dynamics of phase space attractors reconstructed from time series taken at various spatial locations within the developing flow field. The two techniques used for this were the Grassberger- Procaccia dimension and the Lyapunov exponent. Reconstruction of the attractors was performed using the minimum mutual information function. The flow complexity was used in conjunction with Turbulent Intensitites within the flow and the development of the flow velocity profile, to provide a comprehensive picture of the flow field development for pulsed vortex flows. In addition, the techniques from the field of non-linear dynamics were thoroughly tested in the experimental environment. The problem of noise, and its effect on the results produced has been analysed in detail